An experimental study was performed to assess the influences of aluminum content on the porosity, microstructure and mechanical properties of powder metallurgy steels. Optical microscope equipped with the image processing software and the scanning electron microscope were employed to study the microstructure of investigated specimens. In order to find mechanical properties of specimens, Vickers hardness and compression tests were conducted. By increasing the aluminum content (from 0 to 4 wt. %), the porosity increases (from 6.01% to 8.43%). The microstructure of specimens contains aluminum phase distributed between the boundaries of agglomerated iron particles, ferrite, and pearlite. By increasing the aluminum content, stress-strain curves shift significantly downwards, and the modulus of elasticity, elongation, yield stress, and Vickers hardness reduce from 1.82 to 0.86 GPa, 32.1 to 17.8%, 138.1 to 28.2 MPa, and 127.7 to 26.8 HV, respectively.